LED lighting system

Abstract

The invention relates to LED lighting system comprising a power supply circuit and one or more LED modules. The power supply circuit is equipped with input terminals (K 1 , K 2 ) for connection to a supply voltage source and first and second output terminals (K 3 , K 4 ), and a driver circuit (I, II) coupled between the input terminals and the first and second output terminals for generating a LED current. The driver circuit (I, II) comprises a driver control circuit (II) equipped with an input terminal (K 7 ) for increasing or decreasing the LED current in dependency of a signal present at the input terminal of the driver control circuit. The one or more LED modules comprise first and second input terminals (K 5 , K 6 ) for connection to respectively the first and second output terminals of the power supply circuit, a series arrangement of a LED load (LS) and a current sensor (R 1 ) coupled between the input terminals, a module control circuit for generating a current control signal at an output terminal of the module control circuit and coupled to the current sensor and to a reference signal generator (R 3 , R 4 , R 5 , Z 1 ) for generating a reference signal representing a desired magnitude of the LED current, wherein the current control signal has a first value in case the desired value of the LED current is lower than the measured value of the LED current and a second value in case the desired value of the LED current is higher than the measured value of the LED current, and coupling circuitry (D 1 ; Sg, DC, C 1 , C 2 ) coupled during operation between the output terminal of the module control circuit and the input terminal of the driver control circuit, for communicating the first value of the current control signal to the input terminal of the driver control circuit and for blocking the second value, and wherein the signal at the input terminal of the driver control circuit has a default value when all the current control signals have their second value.

The invention claimed is: 
     
       1. An LED light system comprising a power supply circuit and one or more LED modules, wherein the power supply circuit comprises:
 input terminals for connection to a power supply source and first and second output terminals 
 a driver circuit coupled between the input terminals and the first and second output terminals for generating a LED current, the driver circuit comprising a driver control circuit equipped with an input terminal for increasing or decreasing the LED current in dependency of a signal present at the input terminal of the driver control circuit, 
 and wherein each of the one or more LED modules comprises: 
 first and second input terminals for connection to respectively the first and second output terminals of the power supply circuit, 
 a series arrangement of a LED load and a current sensor coupled between the input terminals, 
 a module control circuit for generating a current control signal at an output terminal of the module control circuit and coupled to the current sensor and to a reference signal generator for generating a reference signal representing a desired magnitude of the LED current, wherein the current control signal has a first value in case the desired magnitude of the LED current is lower than a measured value of the LED current and a second value in case the desired value of the LED current is higher than the measured value of the LED current, and 
 a coupling circuit during operation coupled between the output terminal of the module control circuit and the input terminal of the driver control circuit, for communicating the first value of the current control signal to the input terminal of the driver control circuit and for blocking the second value, and 
 wherein the signal at the input terminal of the driver control circuit has a default value when all the current control signals from the one or more modules have their second value. 
 
     
     
       2. The LED light system as claimed in  claim 1 , wherein the coupling circuit comprises a conductive string comprising a unidirectional element, such as a diode, that blocks the second value of the current control signal and conducts the first value of the current control signal. 
     
     
       3. The LED light system as claimed in  claim 1 , wherein the default value is chosen such that the LED current is increased when the signal present at the input of the driver control circuit has the default value. 
     
     
       4. The LED light system as claimed in  claim 1 , wherein the LED module comprises a signal generator coupled between the output of the module control circuit and the first input terminal of the LED module, for generating a communication signal and for coupling the communication signal to the first input terminal in case the current control signal has its first value, and wherein the power supply circuit comprises a detection circuit coupled between the input terminal of the driver control circuit and the first output terminal of the power supply circuit for detecting the communication signal and for controlling the signal at the input terminal of the driver control circuit so that the LED current is decreased in case the communication signal is detected and increased in case the detection circuit does not detect the communication signal, wherein the coupling circuit is formed by the signal generator and the detection circuit. 
     
     
       5. The LED light system as claimed in  claim 1 , wherein the LED system comprises two or more LED modules. 
     
     
       6. The LED light system as claimed in  claim 1 , wherein the LED lighting system comprises a parameter sensor for sensing a parameter and for generating a current control signal at an output terminal of the parameter sensor equal to the first value or the second value of the current control signal generated by the module control circuits of the LED modules in dependency of the result of the sensing, wherein the output terminal of the parameter sensor is coupled to the input terminal of the driver control circuit via a coupling circuit for conducting the first value and blocking the second value of the sensor signal, and wherein the parameter is chosen from a group comprising the total intensity of the ambient light and the light generated by the LED lighting system, the temperature at a particular spot in the LED lighting system, the presence of persons in the vicinity of the LED lighting system and a signal from a remote control. 
     
     
       7. The LED light according to  claim 6 , wherein the coupling circuit of the parameter sensor comprises a unidirectional element. 
     
     
       8. The LED light system as claimed in  claim 4 , wherein coupling circuit of the parameter sensor comprises a signal generator coupled between the output terminal of the parameter sensor and the first output terminal of the power supply circuit, for generating a communication signal and for coupling the communication signal to the first output terminal of the power supply circuit. 
     
     
       9. The LED light system as claimed in  claim 1 , wherein the module control circuit comprises a comparator having a first input terminal coupled to the current sensor and having a second input terminal coupled to the reference signal generator. 
     
     
       10. The LED light system as claimed in  claim 9 , wherein one of the input terminals of the comparator is coupled to an output terminal of a current source generating a temperature dependent current. 
     
     
       11. The LED light system as claimed in  claim 1 , wherein the reference signal generator comprises a zener diode. 
     
     
       12. A method for operating at least one LED module comprising a LED load by means of a driver circuit comprised in a power supply circuit, the method comprising the following steps:
 providing a module control circuit in each LED module for generating a current control signal in dependency of a measured magnitude of a LED current and a desired magnitude of the LED current, the current control signal having a first value in case the desired value of the LED current is lower than the measured value of the LED current and a second value in case the desired value of the LED current is higher than the measured value of the LED current, 
 providing a driver control circuit in the power supply circuit, 
 wherein the driver control circuit is equipped with an input terminal, for increasing or decreasing the LED current in dependency of a signal present at the input terminal of the driver control circuit and, 
 adjusting the signal at the input terminal of the driver control circuit in dependency of the current control signal.